This trial is designed to evaluate survival as well as a number of secondary outcomes (hospitalization for cardiovascular disease, infection, or other non-access-related causes, declining body weight, or declining serum albumin level) in patients randomly assigned to one of four groups: (A) moderate-dose dialysis, low-flux cellulose membrane, (B)high-dose dialysis, low-flux cellulose membrane, (C) moderate-dose dialysis, high- flux synthetic membrane, (D)high-dose dialysis, high-flux synthetic membrane. Each Clinical Center will randomize sufficient patients among these 4 groups such that at least 60 patients are enrolled at all times. The patients will be followed for a 5-year period, replacing deaths or dropouts as they occur with new patients. An 18-month recruitment phase is followed by a 5-year follow-up/intervention phase, and a 6-month closeout phase. Our Clinical Center is uniquely qualified to successfully participate in this study. It is a partnership between the University of Illinois College of Medicine and West Suburban Kidney Centers, a corporation of 14 dialysis units treating 1400 patients in the Chicago area. The study will be performed at the University of Illinois dialysis unit, as well as in 3 nearby units of the WSKC. According to the patient eligibility criteria set out by the Draft MMHD Protocol, we already have identified 220 patients in these 4 units who are eligible for the study and who also meet additional desired criteria (no gross non-compliance, no history of substance abuse, feasibility of delivering a 2-pool Kt/V of 1.4). The centralization of the administrative structure of the WSKC units, which extends through nursing, dietetics, social work, and technologists, and the centralized data gathering systems already in place, will greatly facilitate the coordination among units to complete the study. Appropriate technology to carry out high-efficiency dialysis is in place in each of the primary units. More than 80% of the dialysis stations in the primary units have volumetric UF controlled-machines capable of blood flows > 500 ml/min and dialysate flows of 800 ml/min. A dialyzer reuse program with excellent quality controls allows for use of high efficiency dialyzers which will be necessary to deliver the high-dose dialysis treatments.